I still remember my first pack of Magic the Gathering. By the time I called it quits for good I must have opened several thousand packs, some bought some won. I hardly remember any of those packs. Buying packs was a bad idea anyway. Take them as prizes, sure. But most things I wanted I would either buy or try to bulk trade for.
The pack-busting sensation quickly passed in Hearthstone. I am old enough to know the odds are not in my favor to get cool stuff all the time. However I still know the odds. And the fact that 1% of the time every card can be something super cool still sends a tingle down my spine. The interesting part here is the ability Blizzard gave to disenchant as opposed to trading. This eliminates secondary markets and lets players do something with the cards they do not want for dust which can be used to make cards.
This brought about the idea that each pack is worth 40 dust because a pack at minimum will get you 40 dust. (Five for a common, twenty for a rare. Four commons and one rare are the bare minimum in a pack.) One can do the math but everything seems to work towards getting a bunch of cards to play with, which is making for a game that manages to be enjoyable in several dimensions at the same time.